NOSOCOMIAL INFECTION
DEFINITION
• nosocomial infections are any infection that acquired while in a hospital or healthcare
setting.
• These types of infections are acquired while a patient is admitted to the hospital for
treatment of other conditions.
• Most infections that become clinically evident after 48 hours of hospitalization are
considered hospital-acquired
•
The source of infections are:
1.
other patients,
2.
hospital staff,
3.
contaminated objects or solutions,
4.
from the patient himself (such as transfer from one site of the body to another).
•
Most common nosocomial infections are surgical wound infections, urinary and
respiratory tract infections, and bacteremia (bloodstream infections).
CONTAMINATED SURFACES INCREASE CROSSTRANSMISSION
KNOWN NOSOCOMIAL INFECTION
• Ventilator-associated
pneumonia
• Staphylococcus aureus
• Methicillin resistant
Staphylococcus aureus
• Candida albicans
• Pseudomonas aeruginosa
• Clostridium difficile
• Tuberculosis
• Urinary tract infection
• Hospital-acquired
pneumonia
• Gastroenteritis
• Acinetobacter baumannii
• Vancomycin-resistant
Enterococcus
• Stenotrophomonas
maltophilia
• Legionnaires' disease
REASONS WHY THE PROBLEM EXISTS
• Nosocomial infections are the result of three factors occurring in tandem:
1.
High prevalence of pathogens.
2.
Large numbers of compromised hosts.
3.
Efficient mechanisms of transmission from patient to patient (chain of
transmission).
SITES COMMONLY AFFECTED
• The most common sites affected by nosocomial
infections are:
 urinary tract.
 surgical wounds.
 respiratory tract .
 skin (especially burns).
 blood (bacteremia).
 gastrointestinal tract.
 central nervous system.
RISK FACTORS
• all poor health: advanced age, premature birth, and concurrent conditions
(e.g. chronic obstructive pulmonary disease COPD, diabetes).
• Compromised immunity: Immunodeficiency, immunosuppressive therapy,
irradiation, undernourishment etc..
• Antimicrobial chemotherapy disturbs normal microbial flora populations
(eliminating the competition for pathogens)
• Surgery: openings natural barriers to infection, so microbes can enter
sensitive unprotected tissues and organs.
• Invasive devices: such as intubation tubes, catheters, surgical drains, and
tracheostomy tubes all bypass the body’s natural lines of defense.
MODES OF TRANSMISSION
• Contact transmission.
• Droplet transmission.
• Airborne transmission.
• Common vehicle transmission.
• Vector borne transmission.
MODES OF TRANSMISSION
• Contact transmission is the most important and frequent mode of
transmission of nosocomial infections. It is divided into two subgroups:
• direct contact and indirect contact.
• direct contact
(transfer of microorganisms between a susceptible
host and an infected person)
• Indirect-contact transmission:
Involves contact between a susceptible host and a contaminated intermediate
object, Such objects include contaminated instruments, needles, or dressings, or
contaminated gloves that are not changed between patients.
MODES OF TRANSMISSION
• Droplet transmission:
 Occurs when droplets generated by coughing, sneezing, talking (short distance )
• Airborne transmission:
 Dissemination can be either airborne of evaporated droplets containing microorganisms
that remain suspended in the air for long periods of time) or dust particles containing the
infectious agent.
 Microorganisms carried in this manner can be spread widely by air currents and may
become inhaled by a susceptible host within the same room or over a longer distance
from the source patient, therefore, special air-handling and ventilation are required to
prevent airborne transmission.
 Microorganisms transmitted by airborne transmission include Legionella, Mycobacterium
tuberculosis and the rubeola and varicella viruses.
MODES OF TRANSMISSION
Common vehicle transmission:

"vehicle," such as water, food, air, or the blood supply used by a transfusion
service .
• Vector transmission:
 Occurs when an insect, arthropod, or rodent is the source of infection.
SOURCES OF NOSOCOMIAL INFECTIONS
• The source of the infecting organism may be:
 Exogenous: from another patient or a
member of the hospital staff, or from the
inanimate environment in the hospital.
 Endogenous: from the patient’s own flora.
CAUSES
• The causative microorganisms may be broadly classified into the following
categories:
1.
“Conventional” pathogens that could cause disease in healthy persons
2.
“conditional” pathogens that could cause disease (other than simple
localized infections) only in persons with lowered resistance to infection or
when implanted directly into tissue or normally sterile area.
3.
“Opportunistic” pathogens that could cause severe disease only in patients
with greatly diminished resistance to infection.
CAUSES
MOST COMMON PATHOGENS
• According to the United States National Nosocomial
Infections Surveillance (NNIS) System data, the five most
commonly reported pathogens are:

Escherichia coli (13·7%).
 Staphylococcus aureus (11·2%).

Enterococci (10·7%).

Pseudomonas aeruginosa (10·1%).
 Coagulase-negative staphylococci (9·7%).
CAUSES
• Urinary tract infection: E. coli, enterococci, and P. aeruginosa.
• Surgical wound
staphylococci.
infection:
S.
aureus,
enterococci
and
coagulase-negative
• Bloodstream: coagulase-negative staphylococci, S. aureus, enterococci, E. coli, and
Candida spp.
• Lower respiratory tract infection: S. aureus. P. aeruginosa and Enterobacter spp.
CAUSES
• Among patients in the intensive care unit (ICU) the commonest pathogens were:

P. aeruginosa (12·4%).
 S. aureus (12·3%).

coagulase-negative staphylococci (10·2%).

Candida spp. (10·1%).

Enterobacter spp. and enterococci (8·6% each).
CAUSES
VIRUSES
• There is the possibility of nosocomial transmission
of many viruses, including:
 The hepatitis B and C viruses (transfusions, dialysis, injections, endoscopy).
 Respiratory syncytial virus (RSV), rotavirus, and enteroviruses (transmitted by hand-tomouth contact and via the faecal-oral route).
 Other viruses such as cytomegalovirus, HIV, Ebola, influenza viruses, herpes simplex virus,
and varicella-zoster virus, may also be transmitted.
CAUSES
ACCORDING TO SOURCE
Source
Air
Bacteria
Viruses
Gram-positive cocci
(originating from skin)
Varicella zoster
(chickenpox)
Tuberculosis
Influenza
Fungi
Aspergillus
CAUSES
ACCORDING TO SOURCE
Source
Water
(tap
and
bath)
Bacteria
•Gram-negative bacteria :
Pseudomonas aeruginosa
Aeromonas hydrophilia
Burkholderia cepacia
Stenotrophomonas maltophilia
Serratia marcescens
Flavobacterium
meningosepticum
Acinetobacter calcoaceticus
Legionella pneumophila
•Mycobacteria:
Mycobacterium xenopi
Mycobacterium chelonae
Mycobacterium aviumintracellularae
Viruses
Molluscum
contagiosum
Human
papillomavirus
(bath water)
Noroviruses
Fungi
Aspergillus
Exophiala
jeanselmei
CAUSES
ACCORDING TO SOURCE
Source
Food
Bacteria
Salmonella species
Staphylococcus aureus
Clostridium perfringens
Clostridium botulinum
Bacilluscereus and other
aerobic spore-forming bacilli
Escherichia coli
Campylobacter jejuni
Yersinia enterocolitica
Vibrio parahaemolyticus
Vibrio cholerae
Aeromonas hydrophilia
Streptococcus species
Listeria monocytogenes
Viruses
Rotavirus
Caliciviruses
Fungi
PREVENTION OF NOSOCOMIAL INFECTIONS
Methods of prevention of nosocomial infection (and breaking the chain of
transmission ) include:
• Observance of aseptic technique.
• Frequent hand washing especially between patients.
• Careful handling, cleaning, and disinfection of equipment.
• Where possible, use of single-use disposable items.
• Patient isolation.
PREVENTION OF NOSOCOMIAL INFECTIONS
Methods of prevention of nosocomial infection
(continued):
• Avoidance where possible of medical procedures that can lead with high
probability to nosocomial infection.
• Various institutional methods such as air filtration within the hospital (Architectural
Design).
• General awareness that prevention of nosocomial infection requires constant
personal surveillance.
• Active oversight within the hospital.
PREVENTION OF NOSOCOMIAL INFECTIONS
HAND WASHING
• Proper hand washing is the single most important measure for the Prevention of
nosocomial infections.
• Yet, compliance among healthcare workers is suboptimal ranging from 16% to 81%.
• This is due to a variety of reasons, including:
 Lack of appropriate accessible equipment
 High staff-to-patient ratios
 Allergies to hand washing products.
 Insufficient knowledge of staff about risks and procedures.
 Too long a duration recommended for washing.
PREVENTION OF NOSOCOMIAL INFECTIONS
PROTECTIVE CLOTHING
• Caps and dedicated shoes are required for operating rooms and aseptic units.
• Masks protect staff against airborne pathogens and must be used when
working in the operating room, to care for immunocompromised patients, to
puncture body cavities or perform procedures such as bronchoscopy.
Patients with air-borne pathogens wear masks when outside their isolation
room.
PREVENTION OF NOSOCOMIAL INFECTIONS
PROTECTIVE CLOTHING (GLOVES)
• Sterile gloves for surgery, care for immunocompromised patients, and invasive procedures.
• Non-sterile gloves should be worn for all patient
contacts where hands are likely to be contaminated.
• Hands must be washed when gloves are removed or
changed.
• Disposable gloves should not be reused.
• Latex or polyvinyl-chloride are the materials most
frequently used for gloves.
• Quality and duration of use vary considerably from
one glove type to another.
PREVENTION OF NOSOCOMIAL INFECTIONS
ARCHITECTURAL SEGREGATION
According to the WHO guidelines on infection control,
four areas of a healthcare facility are defined:
• Administrative sections considered as low-risk areas.
• Regular patient wards as moderate-risk areas.
• Intensive care units, burn units, or isolation units as highrisk areas.
• Operating rooms as very high-risk areas.
WHO and others have recommended that traffic flow
should be limited in higher risk areas.
PREVENTION OF NOSOCOMIAL INFECTIONS
ROLE OF THE MICROBIOLOGIST
The microbiologist is responsible for:
• Handling patient and staff specimens to maximize the
likelihood of a microbiological diagnosis.
• Developing guidelines for appropriate collection,
transport, and handling of specimens.
• Ensuring laboratory practices meet appropriate
standards.
• Ensuring safe laboratory practice to prevent infections
in staff.
PREVENTION OF NOSOCOMIAL INFECTIONS
ROLE OF THE MICROBIOLOGIST
• Performing antimicrobial susceptibility testing
following internationally recognized methods, and
providing summary reports of prevalence of
resistance.
• Monitoring sterilization, disinfection and the
environment where necessary.
• Timely communication of results to the Infection
Control Committee or the hygiene officer.
• Epidemiological typing of hospital microorganisms
when necessary.